Composite structures and methods for ablating tissue to form complex lesion patterns in the treatment of cardiac conditions and the like

ABSTRACT

A method of ablating tissue in the heart to treat atrial fibrillation introduces into a selected atrium an energy emitting element. The method exposes the element to a region of the atrial wall and applies ablating energy to the element to thermally destroy tissue. The method forms a convoluted lesion pattern comprising elongated straight lesions and elongated curvilinear lesions. The lesion pattern directs electrical impulses within the atrial myocardium along a path that activates the atrial myocardium while interrupting reentry circuits that, if not interrupted, would cause fibrillation. The method emulates the surgical maze procedure, but lends itself to catheter-based procedures that do not require open heart surgical techniques. A composite structure for performing the method is formed using a template that displays in planar view a desired lesion pattern for the tissue. An array of spaced apart element is laid on the template. Guided by the template, energy emitting and non-energy emitting zones are formed on the elements. By overlaying the elements, the composite structure is formed, which can be introduced into the body to ablate tissue using catheter-based, vascular access techniques.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 08/752,162,filed Nov. 18, 1996, now U.S. Pat. No. 6,241,754, which is a divisionalof application Ser. No. 08/528,805, filed Sep. 15, 1995, now U.S. Pat.No. 5,575,810, which is a continuation of application Ser. No.08/137,672, filed Oct. 15, 1993, now abandoned.

FIELD OF THE INVENTION

In a general sense, the invention is directed to systems and methods forcreating lesions the interior regions of the human body. In a moreparticular sense, the invention is directed to systems and methods forablating heart tissue for treating cardiac conditions.

BACKGROUND OF THE INVENTION

Normal sinus rhythm of the heart begins with the sinoatrial node (or “SAnode”) generating an electrical impulse. The impulse usually propagatesuniformly across the right and left atria and the atrial septum to theatrioventricular node (or “AV node”). This propagation causes the atriato contract.

The AV node regulates the propagation delay to the atrioventricularbundle (or “HIS” bundle). This coordination of the electrical activityof the heart causes atrial systole during ventricular diastole. This, inturn, improves the mechanical function of the heart.

Atrial geometry, atrial anisotropy, and histopathologic changes in theleft or right atria can, alone or together, form anatomical obstacles.The obstacles can disrupt the normally uniform propagation of electricalimpulses in the atria. These anatomical obstacles (called “conductionblocks) can cause the electrical impulse to degenerate into severalcircular wavelets that circulate about the obstacles. These wavelets,called “reentry circuits,” disrupt the normally uniform activation ofthe left and right atria. Abnormal, irregular heart rhythm, calledarrhythmia, results. This form of arrhythmia is called atrialfibrillation, which is a very prevalent form of arrhythmia.

Today, as many as 3 million Americans experience atrial fibrillation.These people experience an unpleasant, irregular heart beat. Because ofa loss of atrioventricular synchrony, these people also suffer theconsequences of impaired hemodynamics and loss of cardiac efficiency.They are more at risk of stroke and other thromboembolic complicationsbecause of loss of effective contraction and atrial stasis.

Treatment is available for atrial fibrillation. Still, the treatment isfar from perfect.

For example, certain antiarrhythmic drugs, like quinidine andprocainamide, can reduce both the incidence and the duration of atrialfibrillation episodes. Yet, these drugs often fail to maintain sinusrhythm in the patient.

Cardioactive drugs, like digitalis, Beta blockers, and calcium channelblockers, can also be given to control the ventricular response.However, many people are intolerant to such drugs.

Anticoagulant therapy also combat thromboembolic complications.

Still, these pharmacologic remedies often do not remedy the subjectivesymptoms associated with an irregular heartbeat. They also do notrestore cardiac hemodynamics to normal and remove the risk ofthromboembolism.

Many believe that the only way to really treat all three detrimentalresults of atrial fibrillation is to actively interrupt all thepotential pathways for atrial reentry circuits.

James L. Cox, M.D. and his colleagues at Washington University (St.Louis, Mo.) have pioneered an open heart surgical procedure for treatingatrial fibrillation, called the “maze procedure.” The procedure makes aprescribed pattern of incisions to anatomically create a convolutedpath, or maze, for electrical propagation within the left and rightatria, therefore its name. The incisions direct the electrical impulsefrom the SA node along a specified route through all regions of bothatria, causing uniform contraction required for normal atrial transportfunction. The incisions finally direct the impulse to the AV node toactivate the ventricles, restoring normal atrioventricular synchrony.The incisions are also carefully placed to interrupt the conductionroutes of the most common reentry circuits.

The maze procedure has been found very effective in curing atrialfibrillation. Yet, despite its considerable clinical success, the mazeprocedure is technically difficult to do. It requires open heart surgeryand is very expensive. Because of these factors, only a few mazeprocedures are done each year.

One objective of the invention is to provide catheter-based ablationsystems and methods providing beneficial therapeutic results withoutrequiring invasive surgical procedures.

Another objective of the invention is to provide systems and methodsthat simplify the creation of complex lesions patterns in body tissue,such as in the heart.

SUMMARY OF THE INVENTION

The intention provides new methods and structures for creating speciallyshaped lesions in heart tissue.

One aspect of the invention provides a method of ablating tissue in theheart to treat atrial fibrillation by introducing into a selected atriuman elongated energy emitting element that can be flexed along its lengthfrom a generally straight shape into a variety of curvilinear shapes.The method exposes the element to a region of the atrial wall whileflexing the element into a desired shape. The method applies ablatingenergy to the element to thermally destroy tissue, forming an elongatedlesion having a contour that follows the flexure of the element. Themethod repeats the tissue exposure, element flexing and energyapplication steps at different spaced regions along the atrial wall. Inthis way, the method forms a convoluted lesion pattern comprisingelongated straight lesions and elongated curvilinear lesions. Thepattern directs electrical impulses within the atrial myocardium along apath that activates the atrial myocardium while interrupting reentrycircuits that, if not interrupted, would cause fibrillation.

In a preferred embodiment, the method introduces the element through avascular approach, without opening the heart. In this embodiment, themethod applies radiofrequency electromagnetic energy to ablate thetissue.

Another aspect of the invention provides a method of ablating tissue inthe heart to treat atrial fibrillation that introduces into a selectedatrium an energy emitting element comprising a three-dimensional arrayof longitudinal main splines. The main splines extend in acircumferentially spaced relationship to form a basket.

According to this aspect of the invention, one or more transverse bridgesplines periodically span adjacent main splines. At least some of themain splines have elongated regions of energy emitting materiallongitudinally spaced among regions of non-energy emitting material. Atleast one of the bridge splines also has a region of energy emittingmaterial that intersects a region of energy emitting material on a mainspline.

According to this aspect of the invention, the method exposes theelement to the atrial wall. The method applies ablating energysimultaneously to at least some of the energy emitting regions of theelement to thermally destroy tissue. The applied ablating energy forms aconvoluted lesion pattern comprising elongated straight and elongatedcurvilinear lesions. The pattern directs electrical impulses within theatrial myocardium along a path that activates the atrial myocardiumwhile interrupting reentry circuits that, if not interrupted, wouldcause fibrillation.

In one embodiment, the method introduces into the selected atrium asecond elongated energy emitting element that can be flexed along itslength from a generally straight shape into a variety of curvilinearshapes. The method exposes the second element to a region of the atrialwall at selected parts of the convoluted lesion pattern, while flexingthe element into a desired shape. The method applies ablating energy tothe second element to thermally destroy tissue to form an elongatedlesion having a contour that follows the flexure of the element. Thiscontoured lesion becomes a part of the convoluted lesion pattern.

In a preferred embodiment, the method introduces the three-dimensionalelement in a collapsed condition through a vascular approach, withoutopening the heart. The method returns the element to itsthree-dimensional shape before exposing it to the atrial wall. In thisarrangement, the method applies radiofrequency electromagnetic energy toablate the tissue.

Another aspect of the invention provides a method of assembling acomposite structure for ablating tissue within the body. The methodcreates a template that displays in planar view a desired lesion patternfor the tissue. The lesion pattern includes a region of elongatedlesions, each having a length that is substantially greater than itswidth. The pattern also includes a region that is free of lesions.

The method lays on the template an array of spaced apart elongatedelements that overlie each region. The method creates energy emittingzones on the elements where the template displays the elongated lesionregion. The method creates non-energy emitting zones on each elementwhere the template displays the lesion-free region.

By joining the elements, the method forms the composite structure.

According to another aspect of the invention, the template displays alesion pattern comprising at least two longitudinal lesion regions, atleast one transverse lesion region intersecting one of the longitudinallesion regions, and a region that is free of lesions. The method thatfollows this aspect of the invention lays on the template an array ofspaced apart longitudinal elements, with at least one longitudinalelement overlying each region where the template displays a longitudinallesion. The method also lays on the template a transverse element thatintersects one of the longitudinal elements and overlies the regionwhere the template displays a transverse lesion.

Guided by the template, this aspect of the invention creates energyemitting and non-energy emitting zones on each longitudinal andtransverse element. The method joins the longitudinal and transverseelements to form the composite structure.

In a preferred embodiment, when joined, the elements form athree-dimensional basket shape.

Yet another aspect of the invention provides catheter-based systems andmethods that create lesions in myocardial tissue. In purpose and effect,the system and method emulate an open heart maze procedure, but do notrequire costly and expensive open heart surgery.

According to this aspect of the invention, the method creates a templatethat displays in planar view a lesion pattern for the myocardium of aselected atrium. The lesion pattern defines a path that directselectrical impulses to activate the myocardium while interruptingreentry circuits that, if not interrupted, would cause atrialfibrillation.

The method lays on the template an array of spaced apart elements.Guided by the template, the method creates energy emitting andnon-energy emitting zones on the elements. The method joins the elementsto form the composite structure.

The method introduces the composite structure into the selected atrium.Upon exposing the composite structure to the atrial myocardium, themethod applies ablating energy to the energy emitting zones to form thedesired lesion pattern in the atrial myocardium.

In a preferred embodiment, the composite structure has athree-dimensional basket shape.

The invention permits the use of a catheter-based techniques thatemulate an open heart maze procedure by tissue ablation, therebyavoiding costly and intrusive open heart surgery. The systems andmethods can be used to perform other curative procedures in the heart aswell.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified and somewhat diagrammatic perspective view of thehuman heart;

FIG. 2 is a diagrammatic plan view of the atrial region of the heart,showing a circuitous path for an electrical impulse to follow betweenthe SA node and the AV node;

FIG. 3 is a grid for creating a three-dimensional structure for makingcurvilinear lesions within the atria of the heart;

FIGS. 4A/4B are splines having electrically conductive and electricallynon-conductive regions that, when assembled, emit ablating energy toform curvilinear lesions within the atria of the heart;

FIGS. 5A/5B are the three-dimensional structures formed when the splinesshown in FIGS. 4A/4B are assembled, with the structure shown in FIG. 5Abeing intended for use within the right atrium and the structure shownin FIG. 5B being intended for use within the left atrium;

FIG. 6 is a perspective, largely diagrammatic view showing theelectrical connections that transmit ablating energy to athree-dimensional structure for forming curvilinear lesions within theatria of the heart;

FIG. 7 is a perspective view of an alternate three-dimensional structurethat can be used to emit ablating energy to form curvilinear lesionswithin the atria of the heart and that includes, as an integral part, asteerable distal element carried within the open interior area of thestructure;

FIG. 8 is a perspective view of an alternate three-dimensional structurethat can be used to emit ablating energy to form curvilinear lesionswithin the atria of the heart and that includes, as an integral part, aninternal electrode structure that comprises a single length of wirematerial preshaped to assume a helical array;

FIG. 9 is a perspective view of an alternate three-dimensional structurethat can be used to emit ablating energy to form curvilinear lesionswithin the atria of the heart and that includes, as an integral part, anexternal electrode structure that comprises a single length of wirematerial preshaped to assume a helical array;

FIG. 10 is a perspective view of an alternate three-dimensionalstructure that can be used to emit ablating energy to form curvilinearlesions within the atria of the heart and that encloses, as an integralpart, an internal basket structure;

FIG. 11 is a plan view of an ablating probe that carries thethree-dimensional basket structure shown in FIG. 7;

FIGS. 12A and 12B are plan views of another ablating probe that carriesa three-dimensional basket structure that, in use, forms curvilinearlesions within the atria of the heart;

FIG. 13 is a plan view of an alternate ablating element that can be usedto emit ablating energy to form curvilinear lesions within the atria ofthe heart;

FIG. 14 is a plan view of an inflatable ablating element that can beused to emit ablating energy to form curvilinear lesions within theatria of the heart;

FIGS. 15 to 26 are views of a delivery system that, when used in themanner shown in these Figures, introduces and deploys ablating elementsshown in the preceding Figures into the atria of the heart;

FIG. 27 is a plan view of a probe that carries a family of flexible,elongated ablating elements that can be used to emit ablating energy toform curvilinear lesions within the atria of the heart;

FIGS. 28 to 30 are views of one flexible, elongated ablating elementthat carries a pattern of closely spaced electrically conductive regionsthat can be used to emit ablating energy to form curvilinear lesionswithin the atria of the heart;

FIG. 31 shows, in somewhat diagrammatic form, a generally straightadjoining lesion pattern that can be formed by the element shown inFIGS. 28 to 30;

FIG. 32 shows, in somewhat diagrammatic form, a curvilinear adjoininglesion pattern that can be formed by the element shown in FIGS. 28 to30;

FIG. 33 show the flexible, elongated ablating element shown in FIG. 28that includes an alternating pattern of conductive regions andnon-conductive regions that can form an interrupted pattern of lesionsin myocardial tissue;

FIG. 34 shows, in somewhat diagrammatic form, an interrupted lesionpattern that can be formed by the element shown in FIG. 33;

FIG. 35 shows, in somewhat diagrammatic form, an interrupted curvilinearlesion pattern that can be formed by the element shown in FIG. 33;

FIGS. 36 to 38 show another embodiment of a flexible, elongated ablatingelement that comprises a closely wound, single layer spiral winding;

FIG. 39 shows, in somewhat diagrammatic form, adjoining lesion patterns,straight and curvilinear, which the element shown in FIGS. 36 to 38 canform;

FIGS. 40 to 45 show a flexible, elongated ablating element that carrieselongated strips of conductive material that can form curvilinearpatterns of lesions in myocardial tissue;

FIG. 46 shows, in somewhat diagrammatic form, adjoining lesion patterns,straight and curvilinear, which the element shown in FIGS. 40 to 45 canform;

FIGS. 47 and 48 show a flexible elongated ablating element that carriesa thin, flat ribbon of spirally wound conductive material that can formcurvilinear patterns of lesions in myocardial tissue;

FIGS. 49 and 50 show a flexible, elongated ablating element thatincludes an elongated opening that exposes a conductive region that canform curvilinear patterns of lesions in myocardial tissue;

FIGS. 51 to 54 show a flexible, elongated ablating element that carriesa wound spiral winding with a sliding sheath that can form curvilinearpatterns of lesions in myocardial tissue;

FIG. 55 shows a handle for the ablating element shown in FIGS. 51 to 54;

FIG. 56 shows a flexible, elongated ablation element, generally likethat shown in FIGS. 51 to 54, with a sheath made of a non rigid materialthat is less flexible that the underlying element;

FIG. 57 shows a flexible, elongated ablation element, generally likethat shown in FIGS. 51 to 54, with a sheath made of a relatively rigidmaterial;

FIG. 58 shows a flexible, elongated alternation element, like that shownin FIGS. 51 to 54, except that it can be operated in a bipolar ablationmode to form curvilinear patterns of lesions in myocardial tissue;

FIG. 59 is a partially diagrammatic view of a system for supplyingablating energy to the element shown in FIG. 28, which includes acontroller that electronically adjusts and alters the energy emittingcharacteristics of the element;

FIG. 60 is a schematic view of the controller and associated input panelshown in FIG. 59;

FIG. 61 is a schematic view of the toggle carried on the input panelshown in FIG. 60 in its three operative positions;

FIG. 62 is a schematic view of the controller shown in FIG. 60electronically configured in its OFF mode;

FIG. 63 is a schematic view of the controller shown in FIG. 60electronically configured to provide a continuous, unipolar lesionpattern;

FIG. 64 is a schematic view of the controller shown in FIG. 60electronically configured to provide an interrupted, unipolar lesionpattern;

FIG. 65 is a schematic view of the controller shown in FIG. 60electronically configured to provide a continuous, bipolar lesionpattern; and

FIG. 66 is a schematic view of the controller shown in FIG. 60electronically configured to provide an interrupted, bipolar lesionpattern.

The invention may be embodied in several forms without departing fromits spirit or essential characteristics. The scope of the invention isdefined in the appended claims, rather than in the specific descriptionpreceding them. All embodiments that fall within the meaning and rangeof equivalency of the claims are therefore intended to be embraced bythe claims.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention provides systems and methods for ablating tissue inside aliving body. The invention creates elongated lesions, which can beeither straight or curvilinear. The invention also creates patterns oflesions, which can be either simple or complex.

The invention lends itself to use in many relatively noninvasivecatheter-based procedures. In contrast with complex, invasive surgicalprocedures, these catheter-based procedures introduce ablation elementsinto interior regions of the body by steering them through a vein orartery.

The Specification that follows focuses upon a particular field of use,which is the treatment of cardiac disease. Still, the diverseapplicability of the invention in other fields of use will also becomeapparent.

FIG. 1 shows a simplified and somewhat diagrammatic perspective view ofthe human heart 10.

The views of the heart 10 shown in FIG. 1 and other Figures in thisSpecification are not intended to be anatomically accurate in everydetail. The Figures show views of the heart 10 in diagrammatic form asnecessary to show the features of the invention.

As will be described in greater detail later, one application of theinvention provides systems and methodologies for forming long,curvilinear ablation patterns inside the heart 10.

The Figures focus upon the details of using the invention to form long,curvilinear lesions for the treatment of atrial fibrillation. It shouldbe appreciated, however, that the invention has applicability for use inother regions of the heart to treat other cardiac conditions. Theinvention also has application in other regions of the body to treatother maladies.

FIG. 1 shows the significant heart chambers and the blood vessels thatservice them. FIG. 1 shows the right and left right atria, respectively12 and 14. FIG. 1 also shows the right and left ventricles, respectively16 and 18.

FIG. 1 further shows the atrial septum 20 that separates the right andleft atria 12/14. FIG. 1 also shows the ventricular septum 21 thatseparates the right and left ventricles 16/18.

As FIG. 1 further shows, the tricuspid valve 22 joins the right atrium12 with the right ventricle 16. The mitral (bicuspid) valve 24 joins theleft atrium 14 with the left ventricle 18.

The superior vena cava 26 (the “SVC”) and the inferior vena cava 28 (the“IVC”) open into the right atrium 12. The pulmonary veins 30 (the“PV's”) open into the left atrium 14. The pulmonary artery 32 leads fromthe right ventricle 16. The aorta 34 leads from the left ventricle 18.

During normal sinus rhythm, blood enters the right atrium 12 through theSVC 26 and the IVC 28, while entering the left atrium 14 through thePV's 30. The atria 12/14 contract, and the blood enters the ventricles16/18 (through the tricuspid and mitral valves 22 and 24, respectively).The ventricles 16/18 then contract, pumping the blood through the aortaand pulmonary arteries 32 and 34.

FIG. 2 shows a diagrammatic plan view of the atrial region of the heart10. FIG. 2 shows the right atrium 12, the left atrium 14, and the atrialseptum 20 dividing the right atrium 12 from the left atrium 14. FIG. 2also shows the approximate location of the orifices of the SVC 26 andthe IVC 28 entering the right atrium 12. FIG. 2 further shows theapproximate location of the orifices of the PV's 30 entering the leftatrium 14.

FIG. 2 also shows the atrial electrophysiology pertinent to thegeneration and treatment of atrial arrhythmias. FIG. 2 shows the SA node36 located near the SVC 26. It also shows the AV node 38.

By folding the left-hand edge of the plan view of FIG. 2 against thecenter septum 20, one forms the three-dimensional contour of the rightatrium 12. By folding the right-hand edge of the plan view of FIG. 2against the center septum 20, one forms the three-dimensional contour ofthe left atrium 14.

FIG. 2 further shows a maze pattern 40 overlaid upon the plan view ofthe right and left atria 12 and 14. The particular maze pattern 40 shownis adopted from one developed by Dr. Cox. See Cox et al., “The SurgicalTreatment of Atrial Fibrillation,” The Journal of CardiovascularSurgery, Vol. 101, No. 4, pp. 569–592 (1991).

The maze pattern 40 directs the sinus impulse from the SA node 36 to theAV node 38 along a specified route. The route that the pattern 40establishes includes a main conduction route 40A that leads circuitouslyfrom the SA node to the AV node. The route also includes multiple blindalleys 40B off the main conduction route 40A.

The pattern 40 is laid out to assure that the sinus impulse activatesmost of the atrial myocardium. Also, the pattern 40 blocks portions ofthe most common reentry circuits around the SVC 26, IVC 28, and the PV's30. The lesion pattern 40 interrupts each of these common reentrycircuits to thereby interrupt the generation of reentry circuits inthese atrial regions.

The invention provides systems and methods for establishing the mazepattern 40, or one like it, without open heart surgery and withoutconventional surgical incisions.

The systems and methods that embody the invention ablate myocardialtissue in the atria. In the process, they form elongated (i.e., long andthin) and sometimes curvilinear lesions (designated “L” in FIG. 2). Thelesions L destroy the myocardial tissue in those regions where reentrycircuits usually occur. Electrical conduction is interrupted in theregions the lesions L occupy.

The presence of the lesions L force electrical impulses emanating in theSA node 36 to follow the open (i.e., not ablated) myocardial regions,which extend between the lesions L. The open regions form a circuitouspath leading from the SA node 36 to the AV node 38, while eliminatingreentry pathways.

In this way, the lesions L prevent atrial fibrillation from occurring.

The lesions L thus serve the same purpose as the incisions made during asurgical maze procedure. However, they do not require an invasive andcostly surgical technique. Instead, according to the invention, thephysician forms the lesions L without opening the heart. Instead, thephysician maneuvers one or more ablation elements through a vein orartery into the atria.

For this purpose, the systems and methods that embody the inventionprovide a family of ablating elements. Numeral 42 generally designateseach individual element in FIGS. 5 to 10 and 25 to 41. In use, theelements 42 form various curvilinear lesion patterns.

In the preferred embodiments, the elements 42 create the lesions L bythermally destroying myocardial tissue by the application ofelectromagnetic energy. In the particular illustrated embodiments, theelements 42 emit radiofrequency electromagnetic energy. Alternatively,microwave electromagnetic energy or light (laser) energy could beemployed for the same purpose.

The direct emission of heat energy by an elongated element by resistanceheating does not form uniformly long, thin lesion patterns as defined bythe invention. Direct heating of an elongated element results in lesionpatterns having regions of charring that offer no therapeutic benefit.

Still, it is believed the invention can be adapted to other ablationtechniques that do not involve the direct contact between a resistanceheated element and tissue. For example, it is believed that long, thin,and curvilinear lesions can be formed by destroying myocardial tissue bycooling or by injecting a chemical substance that destroys myocardialtissue.

The preferred embodiments of the invention provide two generalcategories or types of curvilinear ablating elements 42 that emitradiofrequency energy.

FIGS. 5 to 14 show one preferred category of radiofrequency ablatingelements 42. In this category, the ablating elements 42 make intimatecontact against the atrial wall to create an array of adjoiningcurvilinear lesions L all at once. One of these types of elements 42,once deployed, can form all or substantially all of desired mazepattern. This category of ablating elements will sometimes be identifiedas “category 1 Curvilinear Ablating Elements.”

According to another aspect of the invention, the Category 1 AblatingElements share a common delivery system 44. The delivery system 44introduces and deploys a selected Category 1 Ablating Elements in theatria 12/14.

FIGS. 27 to 55 show another preferred category of radiofrequencyablating elements 42. In this category, the ablating elements 42 makeintimate contact against the atrial wall to create discrete elongated,curvilinear lesions L, one at a time. The physician individually deploysthese ablating elements 42 in succession to form the desired mazepattern. This category of ablating elements will sometimes be identifiedas “Category 2 Curvilinear Ablating Elements.”

Unlike the Category 1 Ablating Elements, the Category 2 AblatingElements do not require a delivery system 44 for introduction anddeployment in the atria 12/14. The Category 2 Ablating Elements aresteerable. They can be introduced into the atria 12/14 like aconventional steerable catheter.

The Delivery System

FIGS. 15 to 26 best show the details of common delivery system 44.

Using the delivery system 44, the physician first introduces a selectedablating element 42 into the right atrium 12 through the femoral vein(as FIG. 20 generally shows). The physician transmits radiofrequencyablating energy through the ablating element 42 to create thecurvilinear lesion L or pattern of lesions L in the myocardium of theright atrium 12.

Once the desired lesion pattern is made in the right atrium, thephysician enters the left atrium 14 through the atrial septum 20 (asFIGS. 25 and 26 generally show). The physician deploys another selectedablating element 42 into the left atrium 14 by puncturing through theatrial septum 20 (as FIG. 26 generally shows). The physician transmitsradiofrequency ablating energy through the ablating element 42 to createthe desired curvilinear lesion L or pattern of curvilinear lesions L inthe myocardium of the left atrium 14.

To carry out the above sequence of steps, the delivery system 44includes an introducer 46 and an outer guide sheath 48 (see FIGS. 15 and16). Both the introducer 46 and the guide sheath 48 are made from inertplastic materials, like polyester.

As FIG. 15 shows, the introducer 46 has a skin-piercing cannula 50. Thephysician uses the cannula 50 to establish percutaneous access into thefemoral vein.

The exposed end of the introducer 46 includes a conventional hemostaticvalve 52 to block the outflow of blood and other fluids from the access.The valve 52 may take the form of a conventional slotted membrane orconventional shutter valve arrangement (not shown).

The hemostatic valve 52 allows the introduction of the outer guidesheath 48 through it, as FIG. 16 shows.

The introducer 46 also preferably includes a flushing port 54 forintroducing anticoagulant or other fluid at the access site, ifrequired.

In the illustrated and preferred embodiment, the delivery system 44 alsoincludes a guide catheter 60 for directing the outer guide sheath 48into the right and left atria 12 and 14.

In one embodiment (see FIG. 16), the guide catheter 60 takes the form ofa conventional steerable catheter with active steering of its distaltip. Alternatively, the guide catheter 60 can take the form of acatheter with a precurved distal tip, without active steering, like aconventional “pig tail” catheter. The catheter with a precurved distaltip is most preferred, because of its simplicity and lower cost.However, for the purposes of this Specification, the details of acatheter with active steering of the distal tip will also be discussed.

As FIG. 16 shows, the steerable catheter 60 includes a catheter body 68having a steerable tip 70 at its distal end. A handle 72 is attached tothe proximal end of the catheter body 68. The handle 72 encloses asteering mechanism 74 for the distal tip 70.

The steering mechanism 74 can vary. In the illustrated embodiment (seeFIG. 17), the steering mechanism is the one shown in U.S. applicationSer. No. 07/789,260, which is incorporated by reference.

As FIG. 17 shows, the steering mechanism 74 of this constructionincludes a rotating cam wheel 76 within the handle 72. An externalsteering lever 78 rotates the cam wheel. The cam wheel 76 holds theproximal ends of right and left steering wires 80.

The steering wires 80 extend along the associated left and right sidesurfaces of the cam wheel 76 and through the catheter body 68. Thesteering wires 80 connect to the left and right sides of a resilientbendable wire or spring (not shown). The spring deflects the steerabledistal tip 70 of the catheter body 68.

As FIG. 16 shows, forward movement of the steering lever 80 bends thedistal tip 70 down. Rearward movement of the steering lever 80 bends thedistal tip 70 up. By rotating the handle 70, the physician can rotatethe distal tip 70. By manipulating the steering lever 80 simultaneously,the physician can maneuver the distal tip 70 virtually in any direction.

FIGS. 18 and 19 show the details of using the steerable catheter 60 toguide the outer sheath 48 into position.

The outer guide sheath 48 includes an interior bore 56 that receives thesteerable catheter body 68. The physician can slide the outer guidesheath 48 along the steerable catheter body 68.

The handle 58 of the outer sheath 48 includes a conventional hemostaticvalve 62 that blocks the outflow of blood and other fluids. The valve62, like the valve 52, may take the form of either a resilient slottedmembrane or a manually operated shutter valve arrangement (not shown).

Together, the valves 52 and 62 provide an effective hemostatic system.They allow performance of a procedure in a clean and relativelybloodless manner.

In use, the steerable catheter body 68 enters the bore 56 of the guidesheath 48 through the valve 62, as FIG. 18 -shows. The handle 58 of theouter sheath 48 also preferably includes a flushing port 64 for theintroduction of an anticoagulant or saline into the interior bore 56.

As FIG. 18 also shows, the physician advances the catheter body 68 andthe outer guide sheath 48 together through the femoral vein. Thephysician retains the sheath handle 58 near the catheter handle 72 tokeep the catheter tip 70 outside the distal end of the outer sheath 48.

In this way, the physician can operate the steering lever 78 to remotelypoint and steer the distal end 70 of the catheter body 68 while jointlyadvancing the catheter body 68 through the femoral vein.

The physician can observe the progress of the catheter body 68 usingfluoroscopic or ultrasound imaging, or the like. The outer sheath 48 caninclude a radio-opaque compound, such as barium, for this purpose.Alternatively, a radio-opaque marker can be placed at the distal end ofthe outer sheath 16.

This allows the physician to maneuver the catheter body 68 through thefemoral vein into the right atrium 12, as FIG. 18 shows.

As FIG. 19 shows, once the physician locates the distal end 70 of thecatheter body 68 in the right atrium 12, the outer sheath handle 58 canbe slid forward along the catheter body 68, away from the handle 72 andtoward the introducer 46. The catheter body 68 directs the guide sheath48 fully into the right atrium 12, coextensive with the distal tip 70.

Holding the handle 58 of the outer sheath 48, the physician withdrawsthe steerable catheter body 68 from the outer guide sheath 48.

The delivery system 44 is now deployed in the condition generally shownin FIG. 20. The system 44 creates a passageway that leads through thefemoral vein directly into the right atrium 12. The delivery system 44provides this access without an invasive open heart surgical procedure.

Alternatively, the outer guide sheath 48 can itself be preshaped with amemory. The memory assumes a prescribed curvature for access to theright or left atrium 12 or 14 through venous access, without need for asteerable catheter 60.

To assist passage through the atrial septum 20, the delivery system 44includes a transeptal sheath assembly 82. The delivery system 44 guidesthe sheath assembly 82 into the right atrium 12 and through the atrialseptum 20 (see FIGS. 25A and 25B) to open access to the left atrium 14.

The delivery system 44 further includes ablation probes 66 to carry aselected ablating element 42. FIG. 20 shows the common structuralfeatures shared by the ablation probes 66. Each ablating probe 66 has ahandle 84, an attached flexible catheter body 86, and a movable hemostatsheath 88 with associated carriage 90. Each ablating probe 66 carries atits distal end a particular type of curvilinear ablating element 42.

Category 1 Curvilinear Ablating Elements

FIGS. 5 to 14 show structures representative of Category 1 CurvilinearAblating Elements 42 that the probes 66 can carry. Elements 42 in thiscategory take the form of various three-dimensional structures, orbaskets 92.

The basket 92 can be variously constructed. In the illustrated andpreferred embodiment, the basket 92 comprises a base member 98 and anend cap 100. An array of generally resilient, longitudinal splines 102extend in a circumferentially spaced relationship between the basemember 98 and the end cap 100. They form the structure of the basket 92.The splines 102 are connected between the base member 98 and the end cap100 in a resilient, pretensed condition.

The basket 92 also include one or more transverse bridge splines 108that periodically span adjacent longitudinal splines 102.

The splines 102/108 collapse into a closed, compact bundle in responseto an external compression force. This occurs when they are capturedwithin the movable hemostat sheath 88, as FIG. 21 shows. As will bedescribed in greater detail later, the splines 102/108 are introducedthrough the delivery system 44 in this collapsed state.

Upon removal of the compression force, the splines 102/108 resilientlyspring open to assume their three-dimensional shape. In this condition,the resilient splines 102/108 bend and conform to the tissue surfacethey contact. The atrial wall is also malleable and will also conform tothe resilient splines 102/108. The splines 102/108 thereby make intimatecontact against the surface of the atrial wall to be ablated, despitethe particular contours and geometry that the wall presents.

In the embodiment shown in FIGS. 5A/5B, six longitudinal splines 102 andsix transverse bridge splines 108 form the basket 92. However,additional or fewer splines 102/108 could be used, depending uponcontinuity and complexity of the maze pattern wanted.

The splines 102/108 can be made of a resilient inert material, likeNitinol metal or silicone rubber. In the illustrated and preferredembodiment, each longitudinal spline 102 is rectangular in cross sectionand is about 1.0 to 1.5 mm wide. The bridge splines 108 are generallycylindrical lengths of material.

As FIGS. 5A/5B best show, the splines 102 include regions 104 that areelectrically conductive (called the “conductive regions”). The splines102 also include regions 106 that are electrically not conductive(called the “nonconductive regions”).

In FIGS. 5A/5B, the bridge splines 108 comprise conductive regions 104along their entire lengths.

The conductive regions 104 function as radiofrequency emittingelectrodes held by the splines 102/108 in intimate contact against theatrial wall. These regions 104 emit radiofrequency ablating energy, whenapplied. The emitted energy forms the curvilinear lesions L in themyocardial tissue that generally conform to the propagation pattern ofthe emitted energy.

The lesions L formed by the conducting electrode regions 104 appear injuxtaposition with normal tissue that the nonconductive regions 106contact. It is this juxtaposition of ablated tissue with normal tissuethat forms the desired maze pattern.

The regions 104/106 can be variously created on the splines 102/108,depending upon the underlying material of the splines 102/108themselves.

For example, when the splines 102/108 are made of an electricallyconductive material, such as Nitinol, the electrically conductiveregions 104 can consist of the exposed Nitinol material itself. Inaddition, the conductive regions 104 can be further coated with platinumor gold by ion beam deposition and the like to improve their conductionproperties and biocompatibility. In this arrangement, insulatingmaterial is applied over regions of the Nitinol metal to form thenonconductive regions 106.

When the splines 102/108 are not made of an electrically conductingmaterial, like silicone rubber, the conductive regions 104 are formed bycoating the exterior surfaces with an electrically conducting material,like platinum or gold, again using ion beam deposition or equivalenttechniques.

FIGS. 5A/5B and 4A/4B purposely exaggerate the diameter differencebetween the electrically conducting regions 104 and electricallynonconducting regions 106 to illustrate them. Actually, the diameterdifference between the two regions 104/106 are approximately 0.05 mm to0.1 mm, which is hard to detect with the naked eye, as FIGS. 7 to 14show with greater realism.

The relative position of the conductive regions 104 and thenonconductive regions 106 on each spline 102, and the spaced apartrelationship of the splines 102 and the bridge splines 108 take in thebasket 92, depend upon the particular pattern of curvilinear lesions Lthat the physician seeks to form.

FIG. 5A shows a basket RA. Upon being deployed in the right atrium 12and used to emit radiofrequency ablating energy, the basket RA createsthe pattern of curvilinear lesions L shown in the left hand (i.e., rightatrium) side of FIG. 2. The basket RA forms this pattern of lesions Lessentially simultaneously when ablating energy is applied to it.

FIG. 5B shows a basket LA. Upon being deployed in the left atrium 14 andused to emit ablating energy, the basket LA creates the pattern ofcurvilinear lesions L shown in the right hand (i.e., left atrium) sideof FIG. 2. Like basket RA, the basket LA forms this pattern of lesions Lessentially simultaneously when ablating energy is applied to it.

FIGS. 3 and 4 generally show the methodology of assembling the splines102/108 into the baskets RA and LA.

As FIG. 3 shows, the splines 102 are first laid out in an equally spacedarrangement upon a template 109. The template 109 displays the desiredlesion pattern for the right and left atria 12 and 14.

FIG. 3 shows splines R1 to R6 laid out upon the template 109 where thelesion pattern for the right atrium 12 is displayed. FIG. 3 showssplines L1 to L6 laid out upon the template 109 where the lesion patternfor the left atrium is displayed.

The template 109 displays longitudinal lesion areas; that is, lesions Lthat run generally vertically on the template 109. The template 109 alsodisplays transverse lesion areas; that is, lesions L that run generallyhorizontally on the template 109. The template 109 also displays areasthat are to be free of lesions L.

Those portions of the splines R1–R6/L1–L6 that overlay a longitudinallesion area must be electrically conducting to ablate tissue. Theseareas of the template 109 identify the electrically conducting regions104 of the splines R1–R6/L1–L6.

Those portions of the splines R1–R6/L1–L6 that do not overlay a desiredlongitudinal lesion area must not be electrically conducting to createlesion-free areas. These areas of the template 109 identify theelectrically nonconductive regions 106 of the splines R1–R6/L1–L6.

Electrically conducting or electrically insulating material aretherefore applied, as appropriate, to the splines to form the regions104/106 the template 109 identifies, as FIGS. 4A and 4B show. FIG. 4Ashows these regions 104/106 formed on the splines R1–R6. FIG. 4B showsthese regions 104/106 formed on the splines L1–L6.

In FIGS. 4A and 4B, the splines are made from an electrically conductingmaterial (i.e., Nitinol), so an electrically insulating material isapplied to form the nonconducting regions 106. The areas free of theelectrically insulating material form the conducting regions 104.

The bridge splines 108 are positioned where the template 109 displaystransverse lesion areas (shown in FIG. 3). The bridge splines 108 aresoldered or otherwise fastened to the adjacent longitudinal splines 102.The bridge splines 108 are electrically conducting to ablate thesetransverse regions of tissue. The transverse lesions link thelongitudinal lesions to create the circuitous bounds of the maze.

The invention therefore forms the template 109 that lays out the desiredlesion pattern. The invention then uses the template 109 to identify andlocate the conductive and nonconductive regions 104 and 106 on thelongitudinal splines R1–R6/L1–L6. The template 109 is also used toidentify and locate the bridge splines 108 between the longitudinalsplines. The baskets RA and LA are then completed by attaching the basemembers 98 and end caps 100 to opposite ends of the longitudinalsplines.

As FIG. 6 shows, each spline 102 is electrically coupled to a signalwire 110 made of an electrically conductive material like copper alloy.The signal wires 110 extend through the base member 98 and catheter body86 into the probe handle 84. Connectors 112 (shown in FIG. 20) attachthe proximal ends of the signal wires 110 to an external source 114 ofablating energy.

The source 114 applies ablating energy to selectively activate all orsome splines 102. The source 114 applies the ablating energy via thesignal wires 110 to create iso-electric paths along the splines 102/108conforming to the desired lesion pattern. Creation of iso-electric pathsalong the splines 102/108 reduces ohmic losses within the probe 66.

As FIG. 6 shows, the applied energy is transmitted by the conductingregions 104 of the splines 102/108. It flows to an exterior indifferentelectrode 116 on the patient.

FIG. 20 shows the introduction of the catheter body 86 of the ablationprobe 66 and its associated ablating element 42. The element 42 takesthe form of basket RA shown in FIG. 5A.

Before introducing the ablation probe 66, the physician advances thehemostat sheath 88 along the catheter body 86, by pushing on thecarriage 90. The sheath 88 captures and collapses the basket RA with it,as FIG. 21 also shows.

As FIG. 22 shows, the physician introduces the hemostat sheath 88, withthe enclosed, collapsed basket RA, through the hemostatic valve 62 ofthe outer sheath handle 58. The sheath 88 and enclosed basket RA enterthe guide sheath 48. The hemostat sheath 88 protects the basket splines102/108 from damage during insertion through the valve 62.

As FIG. 23 shows, when the catheter body 86 of the ablation probe 66advances approximately three inches into the guide sheath 48, thephysician pulls back on the sheath carriage 90. This withdraws thehemostat sheath 88 from the valve 62 along the catheter body 86. Thehemostat valve 62 seals about the catheter body 86. The interior bore 56of the guide sheath 48 itself now encloses and collapses the basket RA,just as the sheath 88 had done.

As FIGS. 23 and 24 show, the guide sheath 48 directs the catheter body86 and attached basket RA of the ablation probe 66 into the right atrium12. As the basket RA exits the distal end of the guide sheath 48, itwill spring open within the right atrium 12, as FIG. 24 shows. Theresilient splines 102/108 bend and conform to the myocardial surface ofthe right atrium 12.

In the illustrated and preferred embodiment (as FIG. 24 shows), thephysician also deploys an ultrasonic viewing probe 118 through thefemoral vein into the right atrium 12, either within our outside theguide sheath 48. Alternatively, fluoroscopy could be used. The physicianoperates the viewing probe 118 to observe the basket RA whilemaneuvering the basket RA to orient it within the right atrium 12. Aidedby the probe 118, the physician can withdraw the basket RA back into theguide sheath 48. The physician can rotate the handle 84 to rotate thebasket RA, and then redeploy the basket RA within the right atrium 12,until the physician achieves the desired orientation for the basket RA.

The physician now takes steps to ablate the myocardial tissue areascontacted by the conducting regions 104 of the basket RA. In this way,the physician forms the desired pattern of lesions L in the right atrium12.

Upon establishing the desired lesion pattern, the physician withdrawsthe ablation probe 66 from the guide sheath 48, by that removing thebasket RA from the right atrium 12. Aided by the viewing probe 118 (asFIG. 25A shows), the physician advances the guide sheath 48 further intothe right atrium 12 into nearness with a selected region of the atrialseptum 20.

To simplify placement of the guide sheath 48 next to the atrial septum20, the physician preferable deploys the steerable catheter body 68through the guide sheath 48 in the manner generally shown in FIGS. 18and 19. Keeping the steerable tip 70 outside the distal end of the outersheath 48, the physician operates the steering lever 78 to remotelypoint and steer the catheter body 68 across the right atrium toward theatrial septum 20, aided by the internal viewing probe 118, or by someexternal ultrasound or fluoroscopic imaging, or both.

Once the physician locates the distal end 70 of the catheter body 68next to the desired site on the atrial septum 20, the physician slidesthe outer sheath 48 forward along the catheter body 68. The catheterbody 68 directs the guide sheath 48 fully across the right atrium 12,coextensive with the distal tip 70 next to the atrial septum 20.

The physician withdraws the steerable catheter body 68 from the outerguide sheath 48 and (as FIGS. 25A and 25B show) advances the transeptalsheath assembly 82 through the now-positioned guide sheath 48 into theatrial septum 20. The viewing probe 118 can be used to monitor theposition of the guide sheath 48 and the advancement of the transeptalsheath assembly 82 toward the atrial septum 20.

As FIG. 25B shows, the transeptal sheath assembly 82 includes a cuttingedge or dilator 122 that carries a sharpened lead wire 120. As thephysician advances the transeptal sheath assembly 82, the lead wire 120forms an initial opening in the septum 20. The dilator 122 enters thisopening, enlarging it and punching through to the left atrium 14 (asFIG. 25B shows).

The Figures exaggerate the thickness of the atrial septum 20. The atrialseptum 20 comprises a translucent membrane significantly thinner thanthe Figures show. This transeptal approach is a well known and widelyaccepted technique used in other left atrium access procedures.

The physician then slides the guide sheath 48 along the transeptalsheath assembly 82 and into the left atrium 14. The physician withdrawsthe transeptal sheath assembly 82 from the guide sheath 48. The guidesheath 48 now forms a path through the femoral vein and right atrium 12into the left atrium 14 (as FIG. 26 shows)

The physician now introduces through the guide sheath 48 the catheterbody 86 of another ablation probe 66 and its associated ablating element42. At this step in the procedure, the ablating element 42 takes theform of basket LA shown in FIG. 5B. The physician advances the hemostatsheath 88 along the catheter body 86, as before described, to captureand collapse the basket LA. The physician introduces the hemostat sheath88, with the enclosed, collapsed basket LA, through the hemostatic valve62 of the outer sheath handle 58, and then withdraws the hemostat sheath88.

Just as FIGS. 23 and 24 show the introduction of the basket RA into theright atrium 12, FIG. 26 shows the guide sheath 48 directing the basketLA into the left atrium 14. As the basket LA exits the distal end of theguide sheath 48, it will spring open within the left atrium 14, as FIG.26 shows.

As FIG. 26 also shows, the physician also deploys the viewing probe 118through the opening made in the atrial septum 20 into the left atrium14. The physician operates the viewing probe 118 while maneuvering thebasket LA to orient it within the left atrium 14. Aided by the probe118, the physician can withdraw the basket LA back into the guide sheath48, rotate the handle 84 to rotate the basket LA, and then redeploy thebasket LA within the left atrium 14. The physician repeats these steps,until the desired orientation for the basket LA is achieved.

The physician now takes steps to ablate the myocardial tissue areascontacted by the conducting regions 104 of the basket LA. In this way,the physician forms the desired pattern of lesions L in the left atrium14.

Upon establishing the desired lesion pattern, the physician withdrawsthe ablation probe 66 from the guide sheath 48, removing the basket LAfrom the left atrium 14. The physician then withdraws the guide sheath48 from the heart and femoral vein. Last, the physician removes theintroducer 46 to complete the procedure.

FIGS. 7 to 14 show alternative embodiments of ablating elements 42(1) to42(7) that the ablation probe 66 can carry. The delivery system 44 asjust described can be used to introduce and deploy each alternativeablating element 42(1) to 42(7) in the same way as baskets RA and LA.

The alternative ablating elements 42(1) to 42(5) shown in FIGS. 7 to 12share many features that are common to that baskets RA and LA shown inFIGS. 5A and 5B. Consequently, common reference numerals are assigned.

The alternative elements 42(1)/(2)/(3)/(4)/(5) all take the form of athree-dimensional basket, designated 92(1), 92(2), 92(3), 92(4), and92(5) respectively.

As before described, each basket 92(1)/(2)/(3)/(4)/(5) comprises a basemember 98 and an end cap 100. As also earlier described, an array ofgenerally resilient, longitudinal splines 102 extend in acircumferentially spaced relationship between the base member 98 and theend cap 100. They form the structure of the baskets 992(1)/(2)/(3)/(4)/(5).

As before described, the splines 102 are made of a resilient inertmaterial, like Nitinol metal or silicone rubber. They are connectedbetween the base member 98 and the end cap 100 in a resilient, pretensedcondition.

Like the baskets RA and LA, the splines 102 of each basket92(1)/(2)/(3)/(4)/(5) collapse for delivery into the atria 12/14 in aclosed, compact bundle (as FIG. 21 generally shows). The splines 102 ofeach basket 92(1)/(2)/(3)/(4)/(5) also resiliently spring open to assumetheir three-dimensional shape when deployed in the atria 12/14, bendingand conforming to the surrounding myocardial tissue surface.

As in the baskets RA and LA (shown in FIGS. 5A/5B), the splines 102 ofeach basket 92(1)/(2)/(3)/(4)/(5) include electrically conductiveregions 104 juxtaposed with electrically nonconductive regions. 106.These regions 104 and 106 are located and formed on the splines 102 ofthe baskets 92(1)/(2)/(3)/(4)/(5) using the same template 109 (shown inFIG. 3) and using the same surface alteration techniques (shown in FIGS.4A/4B). As previously explained, the diameter differences between thetwo regions 104/106 are hard to detect with the naked eye, as FIGS. 7 to10 show.

As before described, the conductive regions 104 function asradiofrequency emitting electrodes that form the curvilinear lesions Lin the tissue that the conductive regions 104 contact. These lesionareas are juxtaposed with normal tissue that the nonconductive regions106 contact.

Instead of the bridge splines 108 that the basket RA and LA carry, thebaskets 92(1)/(2)/(3)/(4)/(5) use alternative assemblies to form thetransverse legion regions spanning adjacent transverse splines 102.

The ablating element 42(1) shown in FIGS. 7 and 11 includes, as anintegral part, a steerable distal element 124 carried within the openinterior area 96 of the basket 92(1). As FIG. 11 shows, the distalelement 124 is itself part of a conventional steerable catheter assembly128 that forms an integral part of the associated ablating probe 66(1).

The distal element 124 carries an electrode 126 comprising a strip ofelectrically conducting material, like Nitinol wire. In use, theelectrode 126 serves as a single movable bridge electrode. In successivemotions controlled by the physician, the single bridge electrode 126 canbe positioned and ablating energy applied to it, to thereby make all thetransverse lesions that the particular maze pattern requires. The singlesteerable bridge electrode 126 of the basket 92(1) thereby serves thefunction of the several fixed bridge splines 108 of the baskets RA andLA.

The bridge electrode 126 can also be used to “touch up” or perfectincomplete lesions patterns formed by the longitudinal splines 102.

The proximal end of the steering assembly 128 of the probe 66(1)includes a handle 130 (as FIG. 11 shows). A guide tube 132 extends fromthe handle 130, through the body 86(1) of the probe 66(1), and into theinterior area 96 of the basket 92(1). The steerable distal element 124and bridge electrode 126 make up the distal end of the guide tube 132.

The handle 130 encloses a steering mechanism 134 for the steerabledistal element 124 and associated bridge electrode 126. The steeringmechanism 134 for the assembly 128 is the same as the steering mechanism74 for the distal tip 70 of the catheter 60 (shown in FIG. 17) and willtherefore not be described again.

By manipulating the steering assembly 128 (as shown by arrows M1, M2,and M3 in FIG. 11), the physician can remotely steer the element 124 andthe associated bridge electrode 126 in three principal directions insidethe basket 92(1) (as shown arrows M1, M2 and M3 in FIG. 7).

First, by remotely pulling and pushing the handle 130, the physicianmoves the element 124 and bridge electrode 126 along the axis of thebasket 92(1), in the direction of arrows M1 in FIGS. 7 and 11.

Second, by remotely rotating the handle 130, the physician rotates theelement 124 and associated bridge electrode 126 about the axis of thebasket 92(1), in the direction of arrows M2 in FIGS. 7 and 11.

Third, by manipulating the steering mechanism 134 by rotating thesteering lever 136 (see FIG. 11), the physician bends the distal element124, and with it, the bridge electrode 126 in a direction normal to theaxis of the basket 92(1), in the direction of arrows M3 in FIGS. 7 and11.

By coordinating lateral (i.e., pushing and pulling) movement of thehandle 130 with handle rotation and deflection of the distal element124, it is possible to move the bridge electrode 126 into any desiredposition, either between any two adjacent longitudinal splines 102 orelsewhere within the reach of the basket 92(1). Preferably, thephysician deploys the interior viewing probe 118 or relies upon anexternal fluoroscopic control technique to remotely guide the movementof the bridge electrode 126 for these purposes.

The ablating element 42(2) shown in FIG. 8 includes, as an integralpart, an internal electrode structure 138 that comprises a single lengthof wire material, such as Nitinol, preshaped to assume a helical array.

In FIG. 8, the helical electrode structure 138 extends from the basemember 98 and spirals within the interior area 96 of the basket 92(2).Along its spiraling path within the basket 92(2), the helical electrodestructure 138 creates interior points of contact 140 with thelongitudinal splines 102. The structure 138 is slidably attached by eyeloops 103 to the splines 102 at these interior points of contact 140.

The helical electrode structure 138 spanning the interior points ofcontact 140 includes regions 146 that are electrically conducting andregions 148 that are not electrically conducting. The precise locationof the regions 146 and 148 along the spiraling path of the electrodestructure 138 will depend upon the pattern of transverse lesionsrequired.

Where a transverse lesion L is required, the structure 138 will includean electrically conducting region 146 between two points of contact 140with adjacent splines 102. The points of contact 140 will also beconducting regions 104. In this way, the structure 138 serves to conductablating energy, when applied, between adjacent splines 102, just as thepresence of the bridge splines 108 did in the baskets RA and LA.

Where a transverse lesion is not required, the structure 138 willinclude an electrically nonconducting region 148 between two points ofcontact 140 with adjacent splines 102. The points of contact 140 willalso be nonconducting regions 106. In this way, the structure 138 willnot conduct ablating energy between adjacent splines 102. The structure138 in these regions 148 serve just as the absence of the bridge splines108 did in the baskets RA and LA.

The electrically conducting regions 146 and electrically nonconductingregions 148 are formed along the helical structure 138 in the same waythe comparable conducting and nonconducting regions 104 and 106 of thelongitudinal splines 102 are formed.

The helical structure 138 captured within the basket 92(2) serves thesame function as the bridge splines 108 of the baskets RA and LA increating zones of transverse lesions.

The shape of the helical structure 138, its interior points of contact140 with the longitudinal splines 102, and the location ofthe-conducting and nonconducting regions 146 and 148 are, like thelocation of the regions 104/106 on the longitudinal splines 102,predetermined to create the desired pattern of longitudinal andtransverse legions L when ablating energy is applied.

As with baskets RA and LA, these considerations for the basket 92(2)will require a particular arrangement of elements for use in the rightatrium 12 and another particular arrangement of elements for use in theleft atrium 14.

The helical electrode structure 138 will collapse laterally upon itselfas the basket 92(2) itself collapses inward in response to an externalcompression force. The basket 92(2) can thereby be introduced into theatria 12/14 in the same manner as the baskets RA and LA. The structure138 will assume its helical shape when the basket 92(2) springs openwith the removal of the compression force. The basket 92(2) can therebybe deployed for use within the atria 12/14 in the same manner as thebaskets RA and LA.

The ablating element 42(3) shown in FIG. 9 is similar in many respectsto the ablating element 42(2) shown in FIG. 8. The ablating element42(3) includes, as an integral part, an internal electrode structure142. Like the structure 138 shown in FIG. 8, the structure 42(3)comprises a single length of wire material, such as Nitinol, preshapedto assume a helical array.

In FIG. 9, like the structure 138 in FIG. 8, the helical electrodestructure 142 extends from the base member 98. However, unlike thestructure 138 shown in FIG. 8, the structure 142 in FIG. 9 spiralsoutside along the exterior surface of the basket 92(3). Like thestructure 138, the structure 142 is slidably attached by eye loops 103to the splines 102 at the exterior points of contact 144.

In other respects, the helical structure 138 and the helical structure142 are essentially identical. Similar to the structure 138, the helicalstructure 142 spanning the points of contact 144 includes regions 146that are electrically conducting and regions 148 that are notelectrically conducting, depending upon the pattern of transverselesions required. Where a transverse lesion L is required, the structure142 will include an electrically conducting region 146. Similarly, wherea transverse lesion is not required, the structure 142 will include anelectrically nonconducting region 148.

The electrically conducting regions 146 and electrically nonconductingregions 148 are formed along the helical structure 142 in the same waythe comparable conducting and nonconducting regions 104 and 106 of thelongitudinal splines 102 are formed.

The helical structure 138 carried outside the basket 92(3) serves thesame function as the bridge splines 108 of the baskets RA and LA increating zones of transverse lesions.

As with the structure 138, the shape of the helical structure 142, itsexterior points of contact 144 with the longitudinal splines 102, andthe location of the conducting and nonconducting regions 146 and 148 arepredetermined to create the desired pattern of longitudinal andtransverse legions L when ablating energy is applied.

As with baskets RA and LA, and the basket 42(2), these considerationsfor the basket 92(3) will require a particular arrangement of elementsfor use in the right atrium 12 and another particular arrangement ofelements for use in the left atrium 14.

The helical electrode structure 142, like the structure 138, willcollapse laterally upon itself and spring back and open into itspredetermined shape as the basket 92(3) itself collapses and opens. Thebasket 92(3) can be introduced and deployed into the atria 12/14 in thesame manner as the baskets RA and LA and the basket 92(2).

FIGS. 12A and B show an alternative helical electrode structure 150within a basket 92(4). The basket 92(4) is essentially identical to thebaskets 92(2) and 92(3) previously described. The helical structure 150,like the structures 138 and 142, includes electrically conductingregions 146 and electrically nonconducting regions 148 formed along itslength.

However, unlike the structures 138 and 142 shown in FIGS. 8 and 9, thestructure 150 is not integrally attached to the basket 92(4). Instead,the structure 150 can be remotely moved by the physician between aretracted position near the base member 98 of the associated basket92(4) (as FIG. 12A shows) and a deployed position within the basket92(4) (as FIG. 12B shows).

The structure 150 occupies its retracted position when the basket 92(4)is collapsed within the guide sheath 48 for introduction into theselected atria 12/14, as FIG. 12A shows. The structure 150 is deployedfor use after the basket 92(4) is deployed outside the distal end of theguide sheath 48 for use within the selected atria 12/14, as FIG. 12Bshows.

In this embodiment, the electrode structure 150 comprises a length ofmemory wire, like Nitinol, that is preshaped into the desired helicalshape. The structure 150 is attached to the distal end of a push/pullrod 152 that extends through a bore 153 in the body 154 of an associatedprobe 156. The push/pull rod 152 is attached at its proximal end to aslide control lever 158 that extends from the handle 160 of the probe156. Fore and aft movement of the slide control lever 158 causes axialmovement of rod 152 within the bore 153.

Pulling back upon the slide control lever 158 (as FIG. 12A shows) movesthe rod 152 aft (i.e., toward the handle 160). The aft movement of therod 152 draws the structure 150 out of the basket 92(4) and into thedistal end of the probe body 154. As the structure 150 enters theconfines of the bore 153, it resiliently straightens out, as FIG. 12Ashows.

Pushing forward upon the slide control lever 158 (as FIG. 12B shows)moves the rod 152 forward (i.e., away from the handle 160). The forwardmovement of the rod moves the structure 150 out of the confines of thebore 153 and into the interior area 96 of the basket 92(4). Since thestructure 150 possesses a resilient memory, it will return to itspreformed helical shape as it exits the bore 153 and enters the basket92(4), as FIG. 12B shows. The resilient memory of the structure 150generally aligns the conductive and nonconductive regions 146 and 148 ofthe structure 150 with the conducting and nonconducting regions 104 and106 of the longitudinal splines 102 to form the desired pattern oflongitudinal and transverse lesions L.

The ablating element 42(5) shown in FIG. 10 includes an external basket92(5) that encloses, as an integral part, an internal basket structure212. The internal basket structure 212 includes-several individualsplines 214 of wire material, such as Nitinol, preshaped to assume athree-dimension array. The individual splines 214 extend from the basemember 98 and transverse prescribed paths. within the interior area 96of the basket 92(5). The several paths the interior splines 214 createinterior points of contact 216 with the longitudinal splines 102 of theexterior basket 92(5). The individual splines 214 are free to move withrespect to the splines 102 at these interior points of contact 216.

The interior basket structure 212 spanning the interior points ofcontact 216.includes regions 218 that are electrically conducting andregions 220 that are not electrically conducting. The precise locationof the regions 218 and 220 along the several paths of the interiorsplines 214 will depend upon the pattern of transverse lesions that isrequired.

Where a transverse lesion L is required, the interior basket structure212 will include an electrically conducting region 218 between twopoints of contact 216 with adjacent exterior splines 102. The points ofcontact 216 will also be conducting regions 104. In this way, theinterior basket structure 212 serves to conduct ablating energy, whenapplied, between adjacent splines 102, just as the presence of thebridge splines 108 did in the baskets RA and LA.

Where a transverse lesion is not required, the interior basket structure212 will include an electrically nonconducting region 220 between twopoints of contact 216 with adjacent exterior splines 102. The points ofcontact will also be nonconducting regions 106. In this way, theinterior basket structure 212 will not conduct ablating energy betweenadjacent exterior splines 102. The interior basket structure 212 inthese regions 220 serve just as the absence of the bridge splines 108did in the baskets RA and LA.

The electrically conducting regions 218 and electrically nonconductingregions 220 are formed along the interior splines 214 in the same waythe comparable conducting and nonconducting regions 104 and 106 of thelongitudinal exterior splines 102 are formed.

The interior basket structure 212 captured within the exterior basket92(5) serves the same function as the bridge splines 108 of the basketsRA and LA in creating zones of transverse lesions.

The shape of the interior basket structure 212, its interior points ofcontact 216 with the longitudinal exterior splines 102, and the locationof the conducting and nonconducting regions 218 and 220 are, like thelocation of the regions 104/106 on the longitudinal splines 102,predetermined to create the desired pattern of longitudinal andtransverse legions L when ablating energy is applied.

As with baskets RA and LA, these considerations for the basket 92(5) andassociated interior basket structure 212 will require a particulararrangement of elements for use in the right atrium 12 and anotherparticular arrangement of elements for use in the left atrium 14.

The interior basket structure 212 will collapse upon itself as theexterior basket 92(5) itself collapses inward in response to an externalcompression force. The double basket 92(5)/212 can be introduced intothe atria 12/14 in the same manner as the baskets RA and LA. The doublebasket 92(5)/212 will reassume its shape when the baskets 92(5)/212spring open with the removal of the compression force. The double basket92(5)/212 can be deployed for use within the atria 12/14 in the samemanner as the baskets RA and LA.

FIG. 13 shows yet another alternative embodiment of an ablating element42(6) that the ablation probe 66 can carry for introduction by thedelivery system 44.

The alternative element 42(6) differs from the previously describedmultiple spline baskets 92(1) to (5) in that it forms a single hoop 162.The hoop 162 allows the physician to form, as part of the lesionpattern, lesions that substantially encircle the orifices of the SVC 26and the IVC 28 in the right atrium 12 and the PV's 30 in the left atrium14 (see FIG. 1). Furthermore, by using one or more hoops 162 insuccession, the physician can eventually form an entire lesion pattern.

As before described, the hoop 162 can be made of a resilient inertmaterial, like Nitinol metal or silicone rubber. It extends from a basemember 164 carried at the distal end of the catheter body of theassociated ablating probe.

The hoop 162 can include electrically conductive regions 104 juxtaposedwith electrically nonconductive regions 106, if needed. Alternatively,the hoop 162 can comprise a single, adjoining conductive region 104.

These regions 104 and 106 are located and formed on the hoop 162 usingthe same surface alteration techniques as before described.

As the baskets 92(1)/(2)/(3)/(4)/(5), the hoop 162 will resilientlycollapse within the guide sheath 48 and resiliently spring open whendeployed outside the guide sheath 48. In this way the hoop 162 can becollapsed for delivery into the atria 12/14 and then be deployed withinthe atria 12/14.

FIG. 14 shows yet another alternative embodiment of an ablating element42(7) that the ablation probe 66 can carry for introduction by thedelivery system 44.

This alternative element 42(7) differs from the previously describedmultiple spline baskets 92(1) to (5) and hoop 162 in that it comprisesan inflatable balloon or bladder 166 made of a thermoplastic polymericmaterial, such as polyethylene. The bladder 166 is formed by either afree-blown process or a mold process.

The bladder 166 carries on its exterior surface a pattern of conductionregions 104 and nonconductive regions 106 to form the desired array oflongitudinal and transverse lesions L.

In the illustrated and preferred embodiment, the conductive regions 104are formed by coating the polymeric material of the bladder 166 with aconductive material. The nonconductive regions 106 are preserved free ofthe conductive material.

Coating of the conductive regions 104 may be accomplished byconventional sputter coating techniques. For example, gold can besputtered onto the exterior surface of the bladder 166. Alternatively, atwo phase sputter coating process may be employed in which an initiallayer of titanium is applied followed by an outer coating of gold. Theprocedure may also use an ion beam assisted deposition (IBAD) process.This process implants the conductive material into the polymer of thebladder 166.

The conductive regions 104 of the bladder 166 are attached to signalwires (not shown) to conduct ablating energy to the conductive regions104.

As with previously described elements 42, the difference in patterns inthe right and left atria will require a particular pattern of conductiveand nonconductive regions 104/106 for use in the right atrium 12 andanother particular arrangement of conductive and nonconductive regions104/106 for use in the left atrium 14.

As FIG. 14 shows, the element 42(6) includes one or more inflationlumens 168 that communicate with the interior of the bladder 166. Thelumens 168 communicate with a common fluid supply tube 172 that extendsthrough the bore of the catheter body 170 of the associated probe 66. Asshown in phantom lines in FIG. 20, the supply tube 172 extends beyondthe probe handle 84 to an injection port 174.

In use, the physician connects the port 174 to a source of fluidpressure (not shown), which is preferably a liquid such as water, salinesolution, or the like. The bladder 166 is deployed in a collapsedposition within the guide sheath 48 using the delivery system 44 alreadydescribed. After maneuvering the distal end of the guide sheath 48 tothe desired location within the right or left atria 12/14, the physiciandeploys the bladder 166 outside the guide sheath 48.

The physician then conducts positive fluid pressure through the supplytube 172 and lumen(s) 168 into the bladder 166. The positive fluidpressure causes the bladder 166 to expand or inflate.

Preferably, the inflation occurs under relatively low pressures ofapproximately 3–10 psi. The inflation is conducted to the extent thatthe bladder 166 is filled, and expanded, but not stretched. Theelectrical conductivity of the conductive regions 104 on the bladder 166is thus not disturbed or impaired. The inflating bladder 166 assumes aprescribed three-dimension shape, just as the baskets 92(1) to 92 (5).The shape can vary, depending upon the shape of the bladder 166. In theillustrated embodiment, the bladder 166 assumes a toroidal shape, withan interior central opening to allow blood flow through it.

Due to its pliant nature, the bladder 166, when inflated, naturallyconforms to the topography of the surrounding atria 12/14 surface, andvice versa, like the baskets 92(1) to 92(4).

By releasing the positive fluid pressure and applying negative pressurethrough the supply tube 172, the physician can drain fluid from thebladder 166. This collapses the bladder 166 for enclosure in the guidesheath 48 for maneuvering within the atria 12/14.

As before described, aided by the viewing probe 118 or other means offluoroscopic or ultrasonic monitoring, the physician can maneuver thebladder 166 within the atria 12/14. Aided by the probe 118, thephysician can repeatedly inflate and deflate the bladder 166 to deployand withdraw the bladder 166 from and into the guide sheath 48, whilerotating it within the guide sheath 48, until the desired orientationfor the bladder 166 within the atria 12/14 is achieved.

The physician now takes steps to ablate the myocardial tissue areascontacted by the conducting regions 104 of the bladder 166. In this way,the physician forms the desired pattern of lesions L in the atria 12/14.

Release of the positive fluid pressure and the application of negativepressure through the supply tube 172 collapses the bladder 166 forenclosure in the guide sheath 48 and removal from the atria 12/14.

Category 2 Curvilinear Ablating Elements

FIGS. 27 to 55 show structures representative of Category 2 CurvilinearAblating Elements 42 that the probes 66 can carry. Elements 42 in thiscategory comprise a family of flexible, elongated ablating elements 176(1) to (5) of various alternative constructions. In the preferred andillustrated embodiments, each element 176 is about 1 to 2.5 mm indiameter and about 1 to 5 cm long.

As FIG. 27 shows, each ablating element 176 is carried at the distal endof a catheter body 178 of an ablating probe 180. The ablating probe 180includes a handle 184 at the proximal end of the catheter body 178. Thehandle 184 and catheter body 178 carry a steering mechanism 182 forselectively bending or flexing the ablating element 176 along itslength, as the arrows in FIG. 27 show.

The steering mechanism 182 can vary. In the illustrated embodiment, thesteering mechanism 182 is like that shown in FIG. 13. The steeringmechanism 182 includes a rotating cam wheel 76 with an external steeringlever 186. As FIG. 13 shows, the cam wheel holds the proximal ends ofright and left steering wires 80. The wires 80 pass through the catheterbody 178 and connect to the left and right sides of a resilient bendablewire or spring within the ablating element 176.

As FIG. 27 shows, forward movement of the steering lever 186 flexes orcurves the ablating element 176 down. Rearward movement of the steeringlever 186 flexes or curves the ablating element 176 up.

In this way the physician can flex the ablating element 176 in eitherdirection along its length. Through flexing, the ablating element 176 ismade to assume a multitude of elongated shapes, from a generallystraight line to a generally arcuate curve, and all intermediatevariable curvilinear shapes between. Through flexing, the ablatingelement 176 can also be brought into intimate contact along its entireablating surface against the surface of the atrial wall to be ablated,despite the particular contours and geometry that the wall presents.

One or more signal wires (not shown) attached to the ablating element176 extend through the catheter body 178 and terminate with an externalconnector 188 carried by the handle 184. The connector 188 plugs into asource of ablating energy (also not shown) to convey the ablating energyto the element 176.

By first remotely flexing the element 176 into the desired curvilinearshape and then applying ablating energy to it, the physician can formboth elongated straight lesions and virtually an infinite variety ofelongated, curvilinear lesions.

In use, the probe 180 and associated flexible ablating element 176 isintroduced into the atria 12/14. Aided by the internal viewing probe 118or another means of fluoroscopic or ultrasonic monitoring, the physicianmanipulates the steering lever 186 to steer the probe 180 into thedesired atrial region.

For entry into the right atrium 12, the physician can direct the probe180 through a conventional vascular introducer through the path shown inFIGS. 18 and 19, without using the delivery system 44. For entry intothe left atrium 14, the physician can direct the probe 180 through aconventional vascular introducer retrograde through the aortic andmitral valves. Preferably, however, the physician can use the deliverysystem 44 to simplify access into the left atrium 14, in the mannershown in FIGS. 25 and 26.

Once in the desired region, the physician uses the same steering lever186 to remotely bend the element 176 into the desired straight orcurvilinear shape into intimate contact with the surrounding atrialwall. By then applying ablating energy to the shaped element 176, thephysician forms a lesion that conforms to that shape.

By repeating this “shape-and-ablate” process within the atria 12/14, thephysician eventually forms a contiguous pattern of straight andcurvilinear lesions along the interior atrial surfaces. These lesionsform the same desired patterns of longitudinal and transverse lesionsthat the three dimensional Category 1 Elements form all at once.

A single variable curvature ablating element 176 can be deployed withinatria of various sizes and dimensions. Furthermore, a single variablecurvature ablating element 176 can be used to form a multitude ofdifferent lesion patterns for the treatment of atrial fibrillation.Therefore, a single variable curvature ablating element 176 possessesthe flexibility to adapt to different atrial geometries and pathologies.

The flexible, elongated ablating element 176 can also be used with aCategory 1 Element to “touch up” or perfect incomplete lesions patternsformed by the Category 1 Element.

FIG. 28 shows one preferred embodiment of a flexible, elongated ablatingelement 176(1). The element 176(1) comprises a flexible body 190 made ofa polymeric material, such as polyethylene. As shown by solid andphantom lines in FIG. 28, the body 190 can be flexed to assumed variouscurvilinear shapes, as just described.

The body 190 carries on its exterior surface a pattern of closely spacedelectrically conductive regions 192. The conductive regions 192 can beformed by coating the polymeric material of the body 190 with aconductive material. The portions 194 of the body 192 between theconductive regions 192 are preserved free of the conductive material.These regions 194 are thereby electrically nonconductive.

Coating of the conductive regions 192 may be accomplished byconventional sputter coating techniques, using gold, for example.Alternatively, an initial layer of titanium can be applied followed byan outer coating of gold using an ion bean assisted deposition (IBAD)process.

Alternatively, the regions 192 can comprise metallic rings of conductivematerial, like platinum. In this embodiment, the rings are pressurefitted about the body 190, which is made from a nonconductive flexibleplastic material, like polyurethane or polyethylene. The portions of thebody 190 between the rings comprise the nonconductive regions 194.

The conductive regions 192 of the body 190 are attached to signal wires(not shown) to conduct ablating energy to one or more of the conductiveregions 192.

The conductive regions 192 can be operated in a unipolar ablation mode,as FIG. 29 shows, or in a bipolar ablation mode, as FIG. 30 shows.

In the unipolar ablation mode (as FIG. 29 shows), each conductive region192 individually serves as an energy transmitting electrode. The energytransmitted by each conductive region 192 flows to an externalindifferent electrode on the patient (not shown), which is typically anepidermal patch. In this made, each conductive region 192 creates itsown discrete lesion. However, due to the close spacing of the conductiveregions 192, the lesions overlap to create a single adjoining lesionpattern.

In the bipolar ablation mode (as FIG. 30 shows), the conductive regions192 are configured as alternating polarity transmitting electroderegions. A first region is designated “+”, and a second region isdesignated “−”. In this mode, ablating energy flows between the “+”electrode regions and the “−” electrode regions. This mode createslesions that span adjacent electrode regions. As in the unipolar mode,the lesions overlap to form a single adjoining lesion pattern.

When operated in either the unipolar ablation mode or the bipolarablation mode, the element 176(1) forms a contiguous lesion pattern P inmyocardial tissue MT along the particular curvature of the body 190.Depending upon the curvature of the body 190, the formed lesion patternP1 in the tissue MT can be straight (as FIG. 31 shows), or the formedlesion pattern P2 in the tissue MT can be curved (as FIG. 32 shows).Both lesion patterns P1 and P2 result from the conformation between theatrial wall and the body 190.

The element 176(1) operates with higher impedance, higher efficiencies,and is more sensitive to tissue contact when operated in the bipolarablation mode than when operated in the unipolar mode.

The lesion pattern created is approximately twice as wide as the body190. The lesion pattern can be made wider by using wider conductiveregions 192.

In a representative embodiment, the body 190 is about 2.5 mm indiameter. Each conductive region 192 has a width of about 3 mm, and eachnonconductive region 194 also has a width of about 3 mm. When eightconductive regions 192 are present and activated with 30 watts ofradiofrequency energy for about 30 seconds, the lesion pattern measuresabout 5 cm in length and about 5 mm in width. The depth of the lesionpattern is about 3 mm, which is more than adequate to create therequired transmural lesion (the atrial wall is generally less than 2mm).

Furthermore, by selectively not activating one or more adjacent regions192, one can create a lesion pattern that is not adjoining, but isinterrupted along the length of the body 190. The interruptions in thelesion pattern provide pathways for propagating the activation wavefrontand serve to control pulse conduction across the lesion pattern.

For example, as FIG. 33 shows, the body 190 includes an alternatingpattern of conductive regions 192 and nonconductive regions 194, eachregion 192/194 being of equal width. By activating some conductiveregions 192 (showed by “A” in FIG. 33), while not activation otherconductive regions (showed by “N” in FIG. 33), an interrupted pattern oflesions PI can be made in myocardial tissue MT, as FIG. 34 shows. AsFIG. 34 also shows, lesions of different length can be formed along theinterrupted pattern PI, depending upon the number of adjacent conductiveregions 192 activated.

Of course, by varying the curvature of the body 190, the interruptedpattern PI can assume a generally straight path (as FIG. 34 shows), orit can assume a generally curved path, as FIG. 35 shows.

FIG. 59 shows a system 298 that couples an ablating energy source 296 tothe energy emitting region 192 of the element 176(1). In the illustratedembodiment, the source 296 supplies electromagnetic radiofrequency (RF)energy to the region 192.

The system 298 includes a controller 300. The controller 300electronically adjusts and alters the energy emitting characteristics ofthe energy emitting region 192.

The controller 300 can electronically configure the energy emittingregion 192 for operation in either a bipolar ablating mode or a unipolarablating mode.

The controller 300 also can electronically configure the energy emittingregion 192 to form lesion patterns having differing physicalcharacteristics. In one mode, the controller 300 configures the energyemitting region 192 to form the continuous lesion pattern P1/P2 shown inFIGS. 31 and 32. In another mode, controller 300 configures the energyemitting region 192 to form a variety of interrupted lesion patterns PI,one of which is shown FIGS. 34 and 35.

The controller 300 includes an input panel 302 for governing theoperation of the controller 300. Through the input panel 302, thephysician chooses the ablation mode and physical characteristics of thelesion patterns. In response, the controller 300 electronicallyconfigures the energy emitting region 192 to operate in the chosenmanner. In this way, the system 298 provides the flexibility to chooseand then electronically create specially shaped lesions virtuallyinstantaneously (i.e., “on the fly”) during an ablation procedure.

The configuration of the controller 300 and associated input panel 302can vary. FIG. 60 diagrammatically shows one preferred arrangement.

In FIG. 60, the element 176(1) includes seven conductive regions,designated E1 to E7, carried on the body 190. Each conductive region E1to E7 is electrically coupled to its own signal wire, designated W1 toW7. The. indifferent electrode, designated EI in FIG. 60, is alsoelectrically coupled to its own signal wire WI.

In this arrangement, the controller 300 includes a switch S_(M) andswitches S_(E1) to S_(E7) that electrically couple the source 296 to thesignal wires W1 to W7. The switch S_(M) governs the overall operatingmode of the regions E1 to E7 (i.e., unipolar or bipolar). The switchesS_(E1) to S_(E7) govern the activation pattern of the regions 192.

Each switch S_(M) and S_(E1 to E7) includes three leads L1; L2; and L3.Electrically, each switch S_(M) and S_(E1 to E7) serves as three-wayswitch.

The three-way switches S_(M) and S_(E1 to E7) are electrically coupledin parallel to the RF energy source 296. The (+) output of the RF source294 is electrically coupled in parallel by a connector 306 to the leadsL1 of the switches S_(E1 to E7). The (−) output of the RF source 294 iselectrically directly coupled by a connector 308 to the center lead L2of the mode selection switch S_(M). A connector 310 electrically couplesin parallel the leads L3 of the switches S_(M) and S_(E1 to E7).

The center leads L2 of the selecting switch S_(E1 to E7) are directlyelectrically coupled to the signal wires W1 to W7 serving the energyemitting regions E1 to E7, so that one switch S_(E(N)) serves only oneenergy emitting region E_((N)).

The lead L1 of the switch S_(M) is directly electrically coupled to thesignal wire WI serving the indifferent electrode EI.

The input panel 302 carries manually operable toggles T_(M) andT_(E1 to E7). One toggle T_(M) and T_(E1 to E7) is electrically coupledto one switch, respectively S_(M) and S_(E1 to E7). When manipulatedmanually by the physician, each toggle T_(M) and T_(E1 to E7) can beplaced in three positions, designated A, B, and C in FIG. 61.

As FIG. 61 shows, toggle Position A electrically couples leads L1 and L2of the associated switch. Toggle Position C electrically couples leadsL2 and L3 of the associated switch. Toggle Position B electricallyisolates both leads L1 and L3 from lead L2 of the associated switch.

Position B of toggle T_(M) and toggles T_(E1 to E7) is an electricallyOFF or INACTIVATED Position. Positions A and B of toggle T_(M) andtoggles T_(E1 to E7) are electrically ON or ACTIVATED Positions.

By placing toggle T_(M) in its Position B (see FIG. 62), the physicianelectronically inactivates the controller 300. With toggle T_(M) inPosition B, the controller 300 conveys no RF energy from the source 296to any region 192, regardless of the position of toggles T_(E1 to E7).

By placing toggle T_(M) in Position A (see FIG. 63), the physicianelectronically configures the controller 300 for operation in theunipolar mode. With toggle T_(M) in Position A, the center lead L2 ofswitch S_(M) is coupled to lead L1, electronically coupling theindifferent electrode EI to the (−) output of the source 296. Thisconfigures the indifferent electrode EI to receive RF energy.

With toggle T_(M) in Position A, the physician electronically configuresthe regions E1 to E7 to emit RF energy by placing the associated toggleT_(E1 to E7) in Position A (as FIG. 63 shows). This electronicallycouples each region E1 to E7 to the (+) output of the source 296,configuring the regions E1 to E7 to emit energy. The indifferentelectrode EI receives the RF energy emitted by these regions E1 to E7.

With toggle T_(M) in Position A and all toggles T_(E1 to E7) in theirPositions A, a continuous, unipolar lesion pattern results, as FIG. 63shows (like that shown in FIGS. 31 and 32).

With toggle T_(M) in Position A, the physician can select toelectronically interrupt the flow of RF energy one or more regions E1 toE7, by placing the associated toggles T_(E1 to E7) in Position B (seeFIG. 64, where the flow is interrupted to regions E3 and E4). As FIG. 64shows, this configuration forms lesions where the regions E1; E2; and E5to E7 emit RF energy next to lesion-free areas where the selected regionor regions E3 and E4 emit no RF energy. An interrupted, unipolar lesionpattern results (like that shown in FIGS. 34 and 35).

Placing toggle T_(M) in Position C (see FIG. 65) electronically isolatesthe indifferent electrode EI from the regions E1 to E7. This configuresthe controller 300 for operation in the bipolar mode.

With toggle T_(M) placed in Position C, the physician can electronicallyalter the polarity of adjacent energy emitting regions E1 to E7,choosing among energy emitting polarity (+), energy receiving polarity(−), or neither (i.e., inactivated).

Toggles T_(E1 to E7) placed in Position A electronically configure theirassociated regions E1 to E7 to be energy emitting (+). TogglesT_(E1 to E7) placed in Position C electronically configure theirassociated regions E1 to E7 to be energy receiving (−). TogglesT_(E1 to E7) placed in Position B electronically inactivate theirassociated regions E1 to E7.

With toggle T_(M) in Position C, sequentially alternating the togglesT_(E1 to E7) between Positions A and C (as FIG. 65 shows) creates acontinuous, bipolar lesion pattern. In FIG. 65, regions E1; E3; E5; andE7 are energy transmitting (+), and regions E2; E4; and E6 are energyreceiving (−).

With toggle T_(M) in Position C, moving selected one or more togglesT_(E1 to E7) to Position B (thereby inactivating the associated regionsE1 to E7), while sequentially alternating the remaining togglesT_(E1 to E7) between Positions A and C (as FIG. 66 shows) creates aninterrupted, bipolar lesion pattern. In FIG. 66, regions E3 and E4 areinactivated; regions E1; E5; and E7 are energy transmitting (+); andregions E2 and E6 are energy receiving (−).

FIG. 36 shows another preferred embodiment of a flexible, elongatedablating element 176(2). The element 176(2) comprises a flexible bodycore 196 made of a polymeric material, such as polyethylene or Teflonplastic. As shown by solid and phantom lines in FIG. 36, the core body196 can be flexed to assumed various curvilinear shapes.

In this embodiment, the core body 196 carries a closely wound, spiralwinding 198.

The winding 198 can comprise a single length of electrically conductingmaterial, like copper alloy, platinum, or stainless steel. Theelectrically conducting material of the winding 198 can be furthercoated with platinum or gold to improve its conduction properties andbiocompatibility.

The winding 198 can also comprise a single length of an electricallynonconducting material, to which an electrically conducting coating,like platinum or gold, has been applied.

The winding 198 can also comprise wound lengths of an electricallyconducting material juxtaposed with wound lengths of an electricallynonconducting material. In this way, the winding 198 can formpredetermined lesion patterns.

When attached to one or more signal wires (not shown), the regions ofthe winding 198 that comprise electrically conducting materials emitablating energy. The winding 198 serves as an elongated flexibleelectrode that can be selectively flexed to form a diverse variety oflong, curvilinear or straight lesion patterns.

Like the element 176(1), the element 176(2) can be operated both in aunipolar ablation mode (as FIG. 37 shows) and in a bipolar ablation mode(as FIG. 38 shows).

In the unipolar ablation mode (as FIG. 37 shows), the winding 198 isformed from a single length of electrically conductive wire. The winding198 serves as an energy transmitting electrode (as designated by apositive charge in FIG. 37). In this arrangement, the winding 198transmits energy into the tissue and to an external indifferentelectrode on the patient (not shown) to form a lesion.

In the bipolar ablation mode (as FIG. 38 shows), the winding 198comprises four wrapped lengths of wire (designated 198(1); 198(2);198(3); and 198(4) in FIG. 38). The wires 198(1) and 198(3) are eachelectrically conducting. The wire 198(2) and 198(4) are not electricallyconducting. Instead, wires 198(2) and 198(4) serve to insulate the wires198(1) and 198(3) from each other.

In the bipolar ablation mode, energy is applied to so that the turns ofthe wire 198(1) serve an energy transmitting regions (designated as“+”), while the turns of the wires 198(3) serve as energy receivingelectrode regions (designated as “−”).

In this mode, ablating energy flows from a transmitting electrode(positive) turn of wire 198(1) to an adjacent receiving electrode(negative) turn of wire 198(3), across the insulating intermediate wires198(2) and 198(4).

When operated in either unipolar or bipolar mode, the element 176(2),like element 176(1), forms a contiguous lesion pattern P in myocardialtissue MT along the curvature of the body 196. As FIG. 39 shows, thelesion pattern P1 can follow a straight path, or the lesion pattern P2can follow a curved path, depending upon the shape given to the body196.

Element 176(2) allows the manufacture of a curvilinear ablation elementof a smaller diameter than element 176(1). The smaller diameter allowsfor the creation of a contiguous lesion pattern of less width and depth.The small diameter of element 176(2) also makes it more flexible andmore easily placed and maintained in intimate contact against the atrialwall than element 176(1).

In a representative embodiment, the element 176(2) is about 1.3 mm indiameter, but could be made as small as 1.0 mm in diameter. The element176(2) is about 5 cm in total length. This element 176(2), whenactivated with 40 watts of radiofrequency energy for 30 seconds, forms acontiguous lesion pattern that is about 3 mm in width, about 5 cm inlength, and about 1.5 mm in depth.

FIGS. 40 to 45 show yet another preferred embodiment of a flexible,elongated ablating element 176(3). Like the other elements 176(1) and176(2), the element 176(3) comprises a flexible body core 200 made of apolymeric material, such as polyethylene. As shown by solid and phantomlines in FIGS. 40 and 43, the core body 200 can also be flexed toassumed various curvilinear shapes.

In this embodiment, the core body 200 carries one or more elongated,exposed strips 202 of flexible, electrically conducting material. Unlikethe circumferential conductive regions 192 of element 176(1) and thecircumferential winding 198 of the element 176(2), the strips 202(1) and202(2) of element 176(3) run parallel along the axis of the core body200.

As FIGS. 40 to 45 show, the parallel strips 202 and the underlying corebody 200 can assume different shapes.

In FIGS. 40 to 42, the core body 200 carries two strips, designatedstrip 202(1)and 202(2). These strips 202(1) and 202(2) are carried closeto each other along the same surface region of the core body 200.

In FIG. 43, the core body 200 carries a single, elongated strip 200 (3).This strip 202(3) has a larger surface area than the individual strips202(1) and 200(2) (shown in FIGS. 40 to 42). However, as will bediscussed later, the strip 202(3) can be operated only in a unipolarablation mode (thereby requiring an external indifferent electrode),whereas the closely spaced pair of strips 202(l)/(2) can be operated ineither a unipolar mode or a bipolar ablation mode.

As FIGS. 44 and 45 show, strips 202(4) and strip 202(5) can occupy allor a significant portion of the core body 200.

In FIG. 44, the strip 200(4) covers the entire exterior surface of thecore body 200. It therefore becomes an elongated variation of thecircumferential regions 192 of element 176(1) and the circumferentialwinding 198 of the element 176(2).

In FIG. 45, multiple strips 200(5) segment the core body 200 intoelongated conducting and nonconducting regions.

The strips 202 shown in FIGS. 40 to 45 can be affixed by adhesive orthermal bonding to the exterior surface of the core body 196, as FIGS.41A/B and 43 to 45 show. Alternatively, the strips 200 can consist ofcoextruded elements of the core body 200 (as FIGS. 40 and 42A/B show).

The strips 202 can comprise elongated lengths of an electricallyconducting material, like copper alloy. The strips can be further coatedwith platinum or gold to improve conduction properties andbiocompatibility. The strips 202 can also comprise a single length of anelectrically nonconducting material to which an electrically conductingcoating, like platinum or gold, has been applied.

Alternatively, the strips 202 can comprise coatings applied byconventional sputter coating or IBAD techniques.

The strips 202 can also have differing cross sectional shapes. In FIGS.41A/B, the strips 202(1) and 202(2) each have a circular cross sectionand thereby present a generally rounded contact zone with the tissue.The FIGS. 42A/B; 44; and 45, the strips 202 have a rectilinear crosssection and thereby present a generally flat contact zone with thetissue.

As FIGS. 41A/B and 42A/B also show, the cross sectional shape of theunderlying core body 200 can also vary. In FIGS. 41A/B, the core body200 has a generally circular cross section. In FIGS. 42A/B, the corebody 200 has a generally flattened region 204, upon which the strips202(1) and 202(2) are laid. The flattened region 204 provides morestable surface contact.

The strips 202(1) and 202(2) can be operated in both a unipolar ablationmode (as FIGS. 41A and 42A show) and in a bipolar ablation mode (asFIGS. 41B and 42B show), depending upon the efficiencies required, asbefore discussed.

When operated in the unipolar mode (see FIGS. 41A and 42A), each strip202(1)and 202(2) serves as elongated, flexible energy emitting electrode(designated with positive charges). The strips 202(3)/(4)/(5) (FIGS. 43to 45) similarly operate as elongated flexible electrodes in theunipolar ablation mode.

When operated in the bipolar mode (see FIGS. 41B and 42B), one strip202(1)/(2) serves as an elongated energy emitting electrode (designatedwith a positive charge), while the other strip serves as an elongatedindifferent electrode (designated with a negative charge).

No matter its particular shape, the element 176(3) forms a contiguous,elongated lesion P in myocardial tissue MT arrayed along the curvatureof the body 200.

As FIG. 46 shows, the lesion P1 in the tissue MT can follow a straightpath, or the lesion P2 can follow a curved path, depending upon theshape of the body 200. In the multiple strip embodiments shown in FIGS.40 to 42, the width of the lesion P1 or P2 can be controlled by thespacing between the strips 202(1)/(2) and 202(5). In the single stripembodiments shown in FIGS. 43 to 45, the width of the lesion P1 or P2can be controlled by the width of the strips 202(3)/202(4)/202(5)themselves.

FIGS. 47 and 48 show still another preferred embodiment of a flexible,elongated ablating element 176(4). Like the other elements 176(1) to(3), the element 176(3) comprises a flexible body core 204 made of apolymeric material, such as polyethylene. As shown by solid and phantomlines in FIG. 40, the core body 204 can also be flexed to assumedvarious curvilinear shapes.

In this embodiment, a thin, flat ribbon 206 of material is spirallywound about and affixed to the core body 204.

The ribbon 206 comprises a polymeric material to which an electricallyconducting coating, like platinum or gold, has been applied.Alternatively, the spiral electrically conductive ribbon 206 can beapplied directly on the core body 204 using an ion beam assisteddeposition (IBAD) process.

The spiral ribbon 206 serves as an elongated flexible electrode. Likethe preceding element 176(1), the element 176(4) can be operated to emitablating energy to form a pattern P1 or P2 of closely spaced lesionsarrayed along the curvature of the body 204, as FIGS. 31 and 32 show.The element 176(4) can be operated only in a unipolar ablation mode inassociation with an external indifferent electrode.

FIGS. 49 and 50 show another preferred embodiment of a flexible,elongated ablating element 176(5). Unlike the other elements 176(1)to(4), the element 176(5) comprises a flexible body core 208 made of anelectrically conducting material. As shown by solid and phantom lines inFIG. 42, the core body 208 can be flexed to assumed various curvilinearshapes.

In this embodiment, the core body 208 is partially enclosed by a shroud210 made from an electrically nonconducting material, like polyethylene.The shroud 210 includes an elongated opening 212 that exposes theunderlying core body 208. The shroud 210 electrically insulates the corebody 208, except that portion 214 exposed through the opening 212.

When ablating energy is applied to the core body 208, only the portion214 exposed through the window 212 emits energy. The rest of the shroud214 blocks the transmission of the ablating energy to the tissue. Theelement 176(5) creates a continuous elongated ablation pattern, likethat shown in FIG. 46 as created by the elongated strip 202(3) shown inFIG. 37.

FIG. 51 shows an ablation probe 246 that carries another type offlexible, elongated ablating element 176(6). In many respects, the probe246 is like the probe 180 shown in FIGS. 27 and 36.

The element 176(6) comprises a flexible body core 222 made of apolymeric material, such as polyethylene or Teflon plastic. The core 222is carried at the distal end of the catheter body 248 of the associatedprobe 246.

The probe 246 includes a handle 250 that carries a steering mechanism252 for flexing the core body 222 into various curvilinear shapes, asshown by solid and phantom lines in FIG. 51. As FIG. 55 shows, thesteering mechanism 252 is like the steering mechanism shown in FIG. 17,already described.

As FIG. 53 shows, the core body 222 carries a closely wound, spiralwinding 224, like that shown in FIG. 36. The winding 224 comprises asingle length of electrically conducting material, like copper alloy orplatinum stainless steel. The electrically conducting material of thewinding 224 can be further coated with platinum or gold to improve itsconduction properties and biocompatibility.

Alternatively, the winding 224 can also comprise a single length of anelectrically nonconducting material, to which an electrically conductingcoating, like platinum or gold, has been applied.

When attached to one or more signal wires (not shown), the winding 224emits ablating energy into the tissue and to an external indifferentelectrode on the patient (not shown). The winding 224 thereby serves asan elongated flexible electrode that can be selectively flexed to form adiverse variety of long, curvilinear or straight lesion patterns, likethose shown in FIG. 39.

Unlike the element 176(2) shown in FIG. 36, the ablating element 176(6)includes a sliding sheath 226 carried about the winding 224 (see FIGS.51 and 52). The sheath 226 is made of an electrically nonconductingmaterial, like polyimide.

The interior diameter of the sheath 226 is greater than the exteriordiameter of the winding 224, so it can be moved axially fore and aftalong the exterior of the winding 224, as shown by the arrows in FIG.52.

As FIG. 53 also shows, the sheath 226 carries a retaining ring 228 onits proximal end. A stylet 230 is attached to the retaining ring 228.The stylet 230 extends from the retaining ring 228, through theassociated catheter body 248, and attaches to a sliding control lever254 carried on the probe handle 250 (see FIG. 55).

Fore and aft movement of the control lever 254 (as arrows in FIG. 55show) imparts, through movement of the stylet 230, fore and aft movementto the sheath 226 in a one-to-one relationship.

The sheath 226 carries a strip 234 of electrically conducting materialat its distal end (see FIG. 53). The strip 234 includes a contact region236 that extends through the sheath 226 to contact one or more turns ofthe underlying winding 224.

A signal wire 238 is electrically connected to the strip 234. The signalwire 238 conveys ablating energy from the source to the winding 224through the contact region 236. The region 236 maintains electricalcontact with the winding 224 during movement of the sheath 226.

The signal wire 238 and strip 234 are enclosed upon the sheath 226 by alayer of electrically insulating shrink tubing 240. A nonconductingadhesive is also used to electrically insulate the signal wire 238 andstylet 230 connections.

By moving the sheath 226 forward, the sheath 226 progressively coversmore of the winding 224. Similarly, by moving the sheath 226 rearward,the sheath 226 progressively exposes more of the winding 224.

The impedance of the ablating element 176(6) varies with the area of thewinding 224 exposed beyond the sheath 226. As progressively less area ofthe winding 224 is exposed beyond the sheath 226, the impedance of theablating element 176(6) becomes progressively greater. Conversely, asprogressively more area of the winding 224 is exposed beyond the sheath226, the impedance of the ablating element 176(6) becomes progressivelyless.

By manipulating the control mechanism 232 on the handle 184, thephysician can thereby remotely adjust the impedance of the ablatingelement 176(6). In this way, the physician gains direct control over theefficiency of the ablation process.

By moving the sheath 226 to expose more or less of the winding 224, thephysician also gains direct control over the size of the ablatingelement 176(6) and, thus, over the size of the curvilinear lesionitself.

By selecting materials of different stiffness for the sheath 226, onecan also alter the bending characteristics of the winding 224.

As FIG. 56 shows, when the sheath 226 is made of a non rigid materialthat less flexible that the underlying core body 222, movement of thesheath 226 over the core body 222 imparts more total stiffness to thebody 222. In this way, the physician can alter the shape of thecurvilinear lesion. The physician can also gain a greater degree oftissue contact with a stiffer flexible body 222.

As FIG. 57 shows when the sheath 226 is made of a relatively rigidmaterial, movement of the sheath 226 effectively changes the fulcrumpoint about which the body core 222 curves. The shape of the body 222,when flexed, therefore changes with movement of the sheath 226.

Further details regarding the concepts of using of a movable sheath tovarying the flexing characteristics of a steerable catheter are revealedin patent application Ser. No. 08/099,843, filed Jul. 30, 1993, andentitled “Variable Curve Electrophysiology Catheter,” now U.S. Pat. No.5,397,321 and patent application Ser. No. 08/100,739, filed Jul. 30,1993 and entitled “Variable Stiffness Electrophysiology Catheter,” nowabandoned.

In one preferred construction, the ablating element 176(6) is about 1.2to 2.0 mm in diameter and about 5 cm long. The outer diameter of thecatheter body 178 that carries the element 176(6) is about 7 French (oneFrench is 0.33 mm). The contact strip 234 measures about 0.05 mm by 0.5mm by 5 mm.

FIG. 58 shows an alternative ablation element 176(6)′, which can beoperated in a bipolar ablation mode. The element 176(6)′ shares manystructural elements with the element 176(6) shown in FIGS. 51 to 54. Thecommon structural elements are identified with the same referencenumbers.

Unlike the element 176(6) shown in FIG. 51, the element 176(6)′ shown inFIG. 58 includes an operative electrode 242 at the distal tip 225 of thecore body 222. Also, unlike the element 176(6) in FIG. 51, the sheath226 of the element 176(6) carries an operative electrode ring 244.

In use, the electrodes 242 and 244 can be maintained at one polarity,while the winding 224 is maintained at the opposite polarity. Thisarrangement makes operation in a bipolar ablation mode possible.

Therefore, along with all the benefits obtained by using the moveablesheath 226 (as already discussed concerning the element 176(6)), theelement 176(6)′ can also obtain the added benefits that bipolar modeoperation provides.

The features of the invention are set forth in the following claims.

1. A tissue ablation device, comprising: a member defining an expandedsize and shape that corresponds to a circumferential region of tissueassociated with an orifice of a vein that carries blood to an atrium;and an ablation element associated with the member and adapted to form acontinuous circumferential lesion in the circumferential region oftissue associated with an orifice of a vein that carries blood to anatrium.
 2. A tissue ablation device as claimed in claim 1, wherein themember comprises a collapsible member.
 3. A tissue ablation device asclaimed in claim 2, wherein the collapsible member comprises acollapsible loop structure.
 4. A tissue ablation device as claimed inclaim 1, wherein the ablation element comprises an energy emittingstructure.
 5. A tissue ablation device as claimed in claim 4, whereinthe ablation element comprises a plurality of spaced energy emittingelements.
 6. A catheter, comprising: a catheter body; and means,associated with the catheter body, for forming a lesion in at least asubstantial portion of a circumferential region of tissue associatedwith an orifice of a vein that carries blood to an atrium.
 7. A catheteras claimed in claim 6, further comprising: a connector adapted toconnect the catheter to an energy source.
 8. A catheter, comprising: acatheter body including at least one energy transmission line; andmeans, operably connected to the at least one energy transmission line,for simultaneously coupling a continuous circumferential region oftissue that surrounds an orifice of a vein that carries blood to anatrium to energy from the at least one energy transmission line.
 9. Acatheter as claimed in claim 8, further comprising: a connector adaptedto connect the at least one energy transmission line to an energysource.
 10. A catheter as claimed in claim 8, wherein the at least oneenergy transmission line comprises a plurality of energy transmissionlines.
 11. A catheter, comprising: a catheter body; and means,associated with the catheter body, for expanding within an atrium,contacting a circumferential region of tissue that surrounds an orificeof a vein that carries blood to the atrium, and forming a continuouslesion in the circumferential region of tissue.
 12. A catheter asclaimed in claim 11, further comprising: a connector adapted to connectthe catheter to an energy source.